Astrocyte diversity and aging in the mouse lemur primate brain

Abstract Astrocytes play key roles in maintaining brain homeostasis, metabolism, and neurovascular integrity, yet their diversity and age-related modulation remain insufficiently understood, particularly across primate lineages. While rodent studies have generated extensive knowledge, notable species differences highlight the need for comparative analyses in non-human primates. The gray mouse lemur ( Microcebus murinus ), a small primate widely used in aging research, offers a valuable but underexplored model for studying astroglial aging. In this study, we characterized astrocyte distribution, morphology, and reactivity in 17 mouse lemurs aged 1.0–11.5 years using GFAP and vimentin immunohistochemistry. We identified marked regional and morphological heterogeneity, with dense astrocytic labeling in white matter, hippocampus, and sparse but diverse cortical populations. Distinct astrocyte subtypes—including fibrous, protoplasmic, projection, pial and subpial interlaminar, radial glia-like cells, tanycytes—were documented. Varicosity-bearing processes were common across multiple astroglial subtypes and may indicate altered physiological states. Quantitative analyses revealed pronounced age-related increases in astrocytic reactivity, particularly in white matter and interlaminar astrocytes. Cortical and hippocampal changes were comparatively modest. These findings indicate region-specific astrocytic vulnerability during aging and support the translational value of the mouse lemur for investigating glial aging in primates. Main Points The mouse lemur is the smallest primate on earth with a key role to understand primate brain characteristics. We characterized seven different astrocyte subtypes: from fibrous to primate-specific astrocyte as interlaminar astrocytes in different brain regions of this primate. Varicosities were reported in different astrocyte subtypes found close to brain borders. Main age-related changes concerned fibrous astrocytes in the white matter and interlaminar astrocytes at the cortical border.